The word "gambit" was originally applied to chess openings in 1561 by Spanish priest Ruy López de Segura, from an Italian expression dare il gambetto (to put a leg forward in order to trip someone). López studied this maneuver, and so the Italian word gained the Spanish form gambito that led to French gambit, which has influenced the English spelling of the word. The broader sense of "opening move meant to gain advantage" was first recorded in English in 1855.[citation needed]

Gambits are often said to be offered to an opponent, and that offer is then said to be either accepted or declined. If a player who is offered a gambit captures the piece (and thus gains material) the gambit is said to be accepted. If the player who was offered the gambit ignores it and instead continues to develop his pieces, then the gambit is said to be declined.

In modern chess, the typical response to a moderately sound gambit is to accept the material and give the material back at an advantageous time. For gambits that are less sound, the accepting player is more likely to try to hold on to his extra material. A rule of thumb often found in various primers on chess suggests that a player should get three moves (see tempo) of development for a sacrificed pawn, but it is unclear how useful this general maxim is since the "free moves" part of the compensation is almost never the entirety of what the gambiteer gains. Of course, a player is not obliged to accept a gambit. Often, a gambit can be declined without disadvantage.

A gambit is said to be 'sound' if it is capable of procuring adequate concessions from the opponent. There are three general criteria in which a gambit is often said to be sound:

Time gain: the player accepting the gambit must take time to procure the sacrificed material and possibly must use more time to reorganize his pieces after the material is taken.

Generation of differential activity: often a player accepting a gambit will decentralize his pieces or pawns and his poorly placed pieces will allow the gambiteer to place his own pieces and pawns on squares that might otherwise have been inaccessible. In addition, bishops and rooks can become more active simply because the loss of pawns often gives rise to open files and diagonals. Former world champion Mikhail Tal once reportedly told Mikhail Botvinnik that he had sacrificed a pawn because it was simply in the way.[2]

Generation of positional weaknesses: finally, accepting a gambit may lead to a compromised pawn structure, holes or other positional deficiencies.

A good example of a sound gambit is the Scotch Gambit: 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4. Here Black can force White to sacrifice a pawn speculatively with 4...Bb4+, but White gets very good compensation for one pawn after 5.c3 dxc3 6.bxc3, or for two pawns after 6.0-0 inviting 6...cxb2 7.Bxb2, due to the development advantage and attacking chances against the black king. As a result, Black is often advised not to try to hold on to the extra pawn. A more dubious gambit is the so-called Halloween Gambit: 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Nxe5?! Nxe5 5.d4. Here the investment (a knight for just one pawn) is too large for the moderate advantage of having a strong center.

This is not a true gambit by Black, since after 4.Nxe5!? Qg5! Black wins material. White can (and from this position should) play a gambit himself with 5.Bxf7+! Ke7 6.0-0! Qxe5 7.Bxg8 Rxg8 8.c3 Nc6 9.d4, when White's two pawns and rolling pawn center, combined with Black's misplaced king, give White strong compensation for the sacrificed bishop.